Gas leakage into or out of drying enclosures presents operational problems as well as health and safety hazards. Drying operations involving noxious gases and/or solvent vapors can leak from inside the enclosure to surrounding work areas. Drying operations carried out under conditions inside the enclosure which are above the upper explosive limit (UEL) require minimum leakage of atmospheric oxygen into the enclosure to avoid fire or explosion hazard. Leakage from the enclosure to the surrounding work area also may present a fire or explosion hazard. Many dryer enclosures are of a split design wherein an upper hood separates from the lower enclosure, providing access to internals for cleaning and maintenance purposes. This point of separation requires a perimeter seal which maintains a gas-tight connection under operating temperatures and pressures.
One conventional hood seal is illustrated in FIG. 1. This arrangement has no provision for expansion movement or reduced conduction heat flow from internal to external surfaces of the enclosure. The gasket material compresses against a flat face with a limited range of compression for movement.
Other prior art seal designs did not allow for expansion and movement of the upper and lower dryer enclosure sections due to thermal expansion. Thus gaps developed under operation conditions which caused leaks at various points around the perimeter seal. Specifically, previous hood and seal designs have been observed to lose seal contact when expansion movements are as little as 1/8 to 1/4 inch. Such movement is common in dryer hoods operating at internal temperatures from 200.degree. F. to 600.degree. F. In the case of flotation dryer hoods, movement of the upper hood relative to the lower hood could also be intentionally introduced in aligning the upper and lower flotation nozzles. Previous seal designs offered very little range for adjustment to accommodate movement of this type.